fbdev/core: Pass Linux device to pm_vt_switch_*() functions

Pass the Linux device to pm_vt_switch_*() instead of the virtual
fbdev device. Prepares fbdev for making struct fb_info.dev optional.

The type of device that is passed to the PM functions does not matter
much. It is only a token within the internal list of known devices.
The PM functions do not refer to any of the device's properties or its
type.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
Cc: Pavel Machek <[e-mail]>
Cc: [e-mail]
Reviewed-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/video/fbdev/core/fbmem.c

···
 		INIT_LIST_HEAD(&fb_info->modelist);
 
 	if (fb_info->skip_vt_switch)
-		pm_vt_switch_required(fb_info->dev, false);
+		pm_vt_switch_required(fb_info->device, false);
 	else
-		pm_vt_switch_required(fb_info->dev, true);
+		pm_vt_switch_required(fb_info->device, true);
 
 	fb_var_to_videomode(&mode, &fb_info->var);
 	fb_add_videomode(&mode, &fb_info->modelist);
···
 
 	device_destroy(fb_class, MKDEV(FB_MAJOR, i));
 
-	pm_vt_switch_unregister(fb_info->dev);
+	pm_vt_switch_unregister(fb_info->device);
 
 	unbind_console(fb_info);